Onchocerciasis in Ecuador. III. Clinical manifestations of the disease in the province of Esmeraldas

Hanging groin and persistent pruritus in a patient from Burkina Faso

Onchocerciasis is a filarial disease caused by Onchocerca volvuvus which can lead to skin, bladder or ocular signs. The authors report a 6-month history of generalized pruritus and two bilateral and symmetric masses in inguinal areas in a 57-year-old black woman. Skin snips and a biopsy of a subcutaneous nodule were diagnosed as onchocerciasis with hanging groin and the patient was treated with ivermectin with a dramatic improvement. If pruritus is the most constant symptom of onchocerciasis, hanging groin is usually observed only in hyperendemic areas in association with high microfilarial density. As no protective immune response is acquired after onchocerciasis, it is recommended that observation is maintained in communities where blindness is less common but where skin manifestations remain prevalent. There is a risk of misdiagnosing onchocerciasis owing to its long incubation period and its unfamiliarity to physicians in nonendemic areas.

Onchocerciasis in Ecuador: infection in children in the Santiago Basin focus, province of Esmeraldas

The prevalence of onchocerciasis infection in children aged 1-12 in the Santiago Basin focus, province of Esmeraldas, Ecuador, was determined to see if active transmission of the disease had occurred in the past 6 years. An infection rate of 45.0% was found. Compared to that found in 1980 (14.5%), the infection rate had increased by 210.1%. The increase was greater on the Rio Santiago (340.5%) than on the Rio Cayapas (195.5%). An increase of 286% was seen in the skin microfilarial density in the 1-4 year age group, with a 56.8% increase in the 5-12 year age group. The prevalence of infection in children aged 0-4 years (those born since the first enquiry in 1980) was 64.3%, with an average skin microfilarial density of 12.2 microfilariae (mf)/mg and with 20% presenting nodules, of which 92.1% occurred in the head region. Of the 34 children examined aged less than one year, 25 (73.5%) were positive for microfilariae with an average microfilarial skin density of 9.6 mf/mg. These data suggest that there is active transmission of the disease in the Santiago Basin onchocercal foci.

Onchocerciasis in the Blue Nile Valley of western Ethiopia

In a survey among 477 inhabitants of the Blue Nile Valley of western Ethiopia 182 (38%) were positive by skin snip investigation for microfilariae of Onchocerca volvulus. Of these only 23% had typical clinical signs and symptoms of onchocerciasis. The highest prevalence rate of microfilariae (84%) was found among Nilotics in the lowlands, where 50% of the children above 10 years, and 90% of adults above 30 years of age, were infected. The mean microfilarial density per skin snip was significantly higher in the high prevalence areas (14) than in the low prevalence areas (3). Positive skin snips from both hip and shoulder were found in 24% of the population, whereas 3% had microfilariae only in the shoulder and 11% only in the hip region. The mean microfilarial density in the hips (16) was double that in the shoulders (8). Ophthalmological evaluation, including slit lamp examination, was possible in 77 of the 182 cases with positive skin snips. Severe eye damage due to onchocerciasis was not observed. However, one 35 year old female had live microfilariae in the anterior chambers of both eyes.

Studies on the biology of Simuliidae (Diptera) at the Santiago onchocerciasis focus in Ecuador, with special reference to the vectors and disease transmission

A survey showed the presence of seven simuliid species in the onchocerciasis focus in Ecuador Simulium exiguum and S. quadrivittatum were the two most common anthropophilic species and were shown to be both experimental and natural vectors of Onchocerca volvulus. S. antillarum only occasionally bit man. Observations were made on the biology of the two vector species and it was evident that S. exiguum was the primary vector of onchocerciasis in the rainy season. The relevance of these findings to the epidemiology and control of onchocerciasis in Ecuador are discussed.